An implant corresponds to a structure that is to be implanted in a bone of a living body for the purpose of treatment. The implant may be used when mounting a prosthesis on the alveolar bone instead of a lost tooth and may also be used when replacing an articular joint of a human body.
A dental implant generally includes an implant body (hereinafter, an implant), an abutment, and a prosthesis. The implant is implanted to a bone structure corresponding to an area where a tooth is lost within the oral cavity. In general, a screw spiral is formed along the outer peripheral surface of the implant. Also, the abutment is tightened to an upper portion of the implant to support the prosthesis that is substantially provided in a tooth shape.
The dental implant is referred to as an osseointegration implant in which the osseointegration is completed. The osseointegration corresponds to a state where a migration is barely observed with bare eyes since the implant surface and newly formed bone tissue directly contact with each other immediately after implantation without biologically having the interposed soft tissue. It generally takes three to six months to complete the above osseointegration after implanting the implant. It is known that the osseointegration should be sufficiently achieved before an occlusion force is applied. When the external force is applied in a state where the sufficient osseointegration is not achieved, the implant surface and the bone structure may not directly contact with each other and, instead, soft tissue may be interposed therebetween, which may result in the failure of osseointegration, that is, the failure of implant. Accordingly, in the case of the conventional implant, it is general not to apply the masticatory pressure to the implant for a predetermined period of time, for example, three to six months after implantation so that sufficient osseointegration may be performed for the outer screw surface of the implant and the bone tissue around the surface.
Human beings have various types of alveolar bones. In many cases, the length and the width of available alveolar bone may be sufficient and osseous tissue may be strong. On the other hand, the length of available alveolar bone may be short or significantly thin. When a tooth is unattended after its extraction for a long period of time, or when a tooth is extracted due to serious gum disease, the alveolar bone may be significantly damaged and only short and thin alveolar bone may remain. In this case, a long implant may not be implanted. For example, in many cases, inferior alveolar nerve and blood vessel pass a lower portion of a tooth portion of a lower jaw, maxillary sinus exists in a tooth portion of an upper jaw, and nostrils exist close to a densincisvus portion of the upper jaw. In this case, when the long implant is to be implanted, a vertically sufficient bone graft may need to be implemented to implant the long implant. The vertical bone graft is difficult and has a very low success rate. A conventional short implant has an insufficient capability for enduring an occlusion force and thus, more implants may need to be implanted and need a longer waiting period than the long implant and thus, may easily fail due to a weak force against the occlusion force.
In a case where an upper portion of alveolar bone is thin, when a conventional implant with a small diameter is implanted to prevent the exposure of the implant, the implant may not endure the occlusion force, thereby causing implant fracture. To prevent the fracture, an implant with a large diameter needs to be implanted. However, when the alveolar bone is thin, a horizontal bone graft operation may be performed to minimize a probable future bone loss. Compared to the vertical bone graft operation, a success rate of the horizontal bone graft operation is relatively high. However, the horizontal bone graft operation may cause greater pain and require long operation time in a patient side and may be hard on a dentist side.
FIG. 1 illustrates a sectional view of a conventional implant 10.
Referring to the conventional implant 10 of FIG. 1, from a distal portion, an end portion of bone tissue of the implant 10, to a proximal portion, a uppermost portion of a body portion to be inserted in bone tissue, a valid diameter of the implant 10 gradually increases or is uniformly maintained and the implant 10 has a maximum diameter in at least the proximal portion. The proximal portion has the largest diameter in order to prevent the implant fracture from occurring in the proximal portion, to prevent the implant from continuously entering the bone tissue when implanting the implant, and to prevent the abutment from loosened.
However, as shown in FIG. 1, an upper portion of the alveolar bone is generally thin and thus, the implant may be externally exposed from the bone structure of the alveolar bone while the implant is implanted or only the thin bone may remain around the proximal portion. In this case, when a prosthesis is installed, a force against an external force may decrease and a greater force may be concentrated on the alveolar bone whereby a bone loss may further quickly occur.
To maintain a bone of the proximal portion is an important factor to guarantee a long-term success of the implant. When the bone fracture continuously occurs in the proximal portion, the proximal portion contained in bone tissue may be gradually exposed. In this case, even with respect to the same occlusion force, a further greater force may be concentrated on an area where the bone fracture has occurred whereby the implant may not endure the occlusion force and the implant may be fractured in this area. Accordingly, it becomes an important issue to maintain the bone of the proximal portion for a long period of time.
Important factors affecting the bone loss in the proximal portion of the implant may include a thickness of bone wrapping around the upper portion, a connection method of the upper portion, and the like.
First, it may be safe when the thickness of bone tissue wrapping around the proximal portion of the implant is to be minimum 1.5 mm-2 mm towards a side. When the thickness of bone tissue becomes to be smaller than 1.5 mm-2 mm, the bone loss may easily occur. As described above, the upper portion of alveolar bone unattended for a long period of time after extraction of a tooth may be thinned. In this case, when the implant of which the diameter of the proximal portion is large is implanted, the bone loss may occur. Therefore, in many cases, a difficult bone graft may need to be accompanied to reinforce the thickness of alveolar bone. Accordingly, if possible within the strength of enduring the occlusion force, the implant of which the diameter of the proximal portion is small may be advantageous to prevent the bone loss.
Second, among the important factors affecting the bone loss in the proximal portion of the implant, corresponds to the method of connecting the proximal portion and the abutment. An integral type in which the implant and the abutment are integrally formed with each other is most safe and has advantages in that a relatively small bone loss occur, a secondary operation is not required, and there is no need to separately connect the abutment. However, in the case of the integral type, the long abutment is exposed to be above the gum and thus, needs to be cut to be suitable for the direction and the length immediately after implantation. In addition, a prosthesis needs to be mounted thereon immediately after implantation. Since the masticatory pressure may be applied immediately after implantation, the weakly implanted implant may easily fail. Accordingly, the integral type is not widely used.
Accordingly, a submerged or non-submerged implant in which the implant and the abutment are separate from each other has been developed. The submerged or non-submerged implant has advantages in that it is safe since the implant can be buried in the gum until the implant is sufficiently adhered to the bone tissue and there is an opportunity of selecting an optimal abutment for the prosthesis. Due to the above reasons, the submerged or non-submerged implant is currently most widely used. However, even the submerged or non-submerged implant still needs the secondary operation in many cases and needs to form a connecting groove within the proximal portion of the implant in order to later connect the abutment to the implant. Therefore, due to the empty inside, the strength may be weakened and the proximal portion may need to be maintained to have a possibly large diameter. In the case of the submerged or non-submerged implant, it is difficult to decrease the diameter of the proximal portion and the inside structure is weak, thereby causing continuous implant fracture by an occlusion force. Also, due to a micro-gap of the connecting portion, the bone loss may increase.
A circumstance where a patient has to make a living for a long period of time without a tooth may bring a mental and physical pain to the patient. In many cases, the patient may not make a normal social life. Accordingly, there is an increasing need for an implant that may reduce a post-operation pain by simplifying an operation if possible, may minimize the aftereffect, and enables a tooth recovery as soon as possible after the operation, thereby enabling a masticatory function, enabling a patient to return to a previous normal social life, and promising a long-term success.